Refrigerating apparatus



Sept. 1955 J. R. HORNADAY ET AL 2,718,121

REFRIGERATING APPARATUS 3 Sheets-Sheet 1 Filed March 27, 1952 J jg jrzaz ames or and jomld H fieeues fi zy-W m Sept. 20, 1955 HORNADAY ET AL2,718,121

REFRIGERATING APPARATUS Filed March 27, 1952 3 Sheets-Sheet 2 -nnsrse amCOLD LIGHT 5W- COMPRESSOR MOTOR L, 6]

- TIMER :1. 0 CK DEFRDST TIMER fnz/erzl or'sl Jams R Horne/day andDonald H fieez/es' Sept. 20, 1955 HORNADAY ET AL 2,718,121

REFRIGERATING APPARATUS 3 Sheets-Sheet 3 Filed March 27, 1952 G/ and.Domlci H flea/es fnvenz ors kfames J f. h orncui Wu III United StatesPatent REFRIGERATING'APPARATUS James R. Hornaday, North Muskegon, andDonald H. Reeves, Muskegon, Mich., assignors to Borg-Warner Corporation,Chicago, Ill., a corporation of Illinois Application March 27, 1952,Serial No. 278,838

4 Claims. (Cl. 624) principal object and accomplishment the provision ofa defrosting system wherein the actual duration of a se lecteddefrosting interval is automatically varied inaccordance with therequirements of the refrigerator instead of being arbitrarily fixed fora definite period of time as in the usual prior art defrosting systems.

More specifically stated, the invention contemplates the provision of adefrosting system for a refrigerator by the employment of heat and anovel control system therefor whereby the heat source is energized by atimed control mechanism and deenergized by a predetermined rise intemperature effecting operation of a thermal responsive means.

To this end the invention seeks to provide an automatic refrigeratorcomprising an evaporator unit and having means normally controlling thecirculation of refrigerant in said evaporator unit, a heating elementdisposed adjacent portions of said evaporator unit and adapted to warmthe refrigerant contained in said evaporator unit, control meansoperable at predetermined intervals to render ineffective the operationof said normal control means and simultaneously therewith controlenergization of said heating element, and thermal responsive means forcontrolling the duration of the period wherein the operation of thenormal means is ineffective and operable to restore control ofcirculation of refrigerant in said evaporator unit to said normalcontrol means.

It is customary in refrigeration to maintain the evaporating means atfreezing temperatures. This causes the accumulation of frost upon theevaporating means which acts as insulation and thereby reduces theefiiciency and capacity of the refrigerating system. It is, therefore,desirable that this accumulation of frost be kept at a minimum andperiodic defrosting of the refrigerating system is necessary.Heretofore, defrosting of the system was accomplished by stopping theapparatus for a period of time and after the accumulation of frost ismelted the refrigerating apparatus is again started, these operationsbeing accomplished manually. It is notable that the starting andstopping of the refrigerating system :for defrosting purposes hasalso-been accomplished by means of a clock mechanism which is adapted tostop the mechanism at regular intervals, this system being clearlyillustrated, for example, in the I. C..Buchanan et al. Patent No.2,429,449 issued October 21, 1947.

Here tofore, automatic defrosting systems have employed time switcheswhich open a circuit, dead or alive, at a certain time and, in likemanner, close at the end of a fixed interval. Such switches have beenknown to be comparatively expensive and requir'erela'tively powerfulclock movements to open and close the switches,

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Moreover, the clock movements were required to be very rugged and strongto open circuits carrying motors under load or receiving initialstarting inrushes.

The present invention contemplates the provision of a cut-out mechanismcombining both mechanical and electro-magnetic action effective to openthe compressor motor circuit during the interval of the defrosting cyclethereby preventing normal circulation of the refrigerant for thatinterval.

It is preferred to provide a daily defrosting cycle of sufiicientaverage duration to defrost the coils, keep the ice drawers and thedrawer frame reasonably free of ice, and yet not long enough to allowthe refrigerator temperature to rise too high for the ice cubes to melt.

It is an important object and accomplishment of the invention to providea novel automatic defrosting system for a refrigerator and which issimple to operate and rugged and reliable in use.

An ancillary object and accomplishment of the invention is to provide anew and improved defrosting mechanism for a refrigerating apparatus andwhich is adapted to be economically manufactured and which is sodesigned as to permit the manufacture and assembly thereof in accordancewith present day large scale mass production manufacturing-methods ofconstruction and assembly.

Another important object and accomplishment of the invention is toprovide "an automatic refrigerating system which includes an evaporatorunit having refrigerant conduits thereon, a refrigerant circulating insaid conduits, heating means disposed adjacent to at least one portionof said refrigerant containing conduits to warm the refrigerantcontained therein, and defrosting means utilizing the circulation ofsaid warmed refrigerant through said conduits to transmit the heat fromthe heating means throughout the refrigerant containing conduits andsaid evaporating unit for defrost purposes.

A further object and accomplishment of the invention is to provide in arefrigerating system including an evaporator unit having conduits forrefrigerant thereon and a refrigerant circulating in said conduits,defrosting means including heating means adjacent to more than oneportion of said conduits for warming the refrigerant and arranged sothat defrosting portions of said conduits are intermediate of saidseveral refrigerant warming portions of the conduits.

- The invention seeks, as a final object and accomplishment, to providea defrosting system of the character indicated and which is particularlycharacterized by a design arrangement to more advantageously andsatisfactorily perform the functions required of it and adapted toprovide a compact unit which will successfully combine-the factors ofstructural simplicity and durability,

I are understood from, the within description.

and yet be economical to manufacture. 1

Additional objects, features and advantages of the invention disclosedherein will be apparent to persons skilled in the art after theconstruction and operation I It is preferred to accomplish the variousobjects of this invention and to practice the same in substantially themanner as hereinafter more fully described, and as more particularlypointed out in the appended claims.

Embodiments of the invention are illustrated in the accompanyingdrawings forming a part hereof and wherein:

Fig. l is a diagrammatic view illustrating the mechanical apparatusemployed in a refrigerating system with which the present defrostermechanism may be adjunctively employed to advantage; Fig. 2 is aperspective view of the defroster system embodying the features of thepresent invention; Fig. 3 is a wiring diagram'disposed compositely uponone form of refrigerator with which the present invention may beadvantageously employed;

Fig. 4 is an elevational view of a heater element which forms animportant component part of the subject defroster system, this viewhaving portions thereof shown in section to more clearly illustrate theinternal construction thereof;

Fig; 5- is a sectional view illustrating a fusible link forming animportant component part of the heater disclosed in Fig. 4; and

Fig. 6 is an exploded view of some of the important component parts ofthe fusible link illustrated in Fig. 5.

Thedrawings' are to be understood to be more or less of a schematiccharacter for the purpose of illustrating, and disclosing a typical orpreferred form of the improvements contemplated herein and in thedrawings like reference characters identify the same parts in theseveral views.

Referring to the drawings, particularly Fig. 1, there is illustrateddiagrammatically a refrigerating apparatus designated in its entirety bythe letter A and which may comprise a motor driven compressor 20, acondenser 21., and an evaporator 22. The described system: may

be of the compressor-condenser-expander type wherein refrigerant iscirculated bymeans of the compressor 20 through the condenser 21 forextracting or dissipating heat from. the refrigerant medium and thenceto a freezer or evaporator 22 in which the refrigerant medium isexpanded or vaporized for absorbing heat and refrigerant medium isthereafter returned to the compressor from whence the cycle is repeated.

The defroster mechanism with which the present invention is particularlyconcerned is illustrated in Fig. 2 and designated in its entirety by thenumeral 30. In Fig. 2 it can be seen that the defroster mechanism isoperatively' associated with the evaporator 22 forming a component partof the refrigerating system A as illustrated in. Fig. 1.

Suflice it to say, since the invention is not particularly concernedwith the precise construction of the refrigerating system A asdiagrammatically illustrated in Fig. 1, and/or its associated parts,they will not be further described in detail, and it is deemedsufficient for all intentions and purposes herein contained to show onlyportions thereof adjacent to and cooperating with the defrosting system30 with which the invention is particularly concerned.

Having thus described, by way of example, a possible adaptation of thedefroster mechanism 30 and the general environment surrounding saidadaptation, the specific details of construction and cooperatingfunctions of the various parts of the defrosting mechanism 30 with whichthe present invention is particularly concerned, will now be describedin detail.

In the exemplary embodiment of the invention de' picted in Fig. 2, thedefrosting mechanism 30 as associated with the evaporator 22, comprises,in general, a refrigerant inlet 31 upper end portions of which arereceived into a refrigerant conduit 33, said inlet and said conduitbeing arranged for cooperative co-action to impart a jet action to therefrigerant as it leaves the inlet and enters the conduit, this being animportant feature of the invention and will be more fully describedhereinafter, a refrigerant conduit 34 forming a continuation of theconduit 33 and formed to define a substan tially serpentine shape as at34a and 34b and disposed in thermal contact with the lower shelf 35 ofthe evaporator 22, a refrigerant conduit 36 as a continuation of therefrigerant conduit 34 but formed to define a vertical leg, arefrigerant conduit 37 forming a continuation of said conduit 36 andformed to define a substantially serpentine shape as at 37a and 37b anddisposed in thermal contact with an intermediate shelf 38 of theevaporator 22, said refrigerant conduit 37 terminating as at 39 into anaccumulator 40, a refrigerant conduit 41 connected bet een said. a cumlator and sa d refrigerant conduit 33, and an electrically operatedheating element 42 disposed adjacent portions of said refrigerantconduit 34 and carried by the evaporator shelf 35, said heater element42 being electrically energized responsive to operation of a timedcontrol mechanism 43 and deenergized responsive to predeterminedtemperature settings of a thermostat element 44 wired in circuit withsaid timed control mechanism and carried by the lower shelf 35 of theevaporator 22 and disposed adjacent said heating element 42.

It is important to note that during the normal refrigerating cycle therefrigerant enters the evaporator 22 from the condenser 21 via therefrigerant inletconduit 31 which discharges as at 32 into therefrigerant conduit 33 where the refrigerant will be forced by a jetaction to continue in its circuitous path through the refrigerantconduit 34 and portions thereof as at 34a and 34b and. then flow intothe refrigerant conduit 36- Which defines. a vertical leg whereby therefrigerant is carried upwardly in the evaporator 22 for dispositioninto a refrigerant conduit 37, the end portions 39 of which open into anaccumulator 40 where the refrigerant may be sucked as at into a suctionline 51 by which it is returned to the compressor 20- and wherein therefrigerant is compressed for a recycle through the system.

For a proper understanding of the important operational concepts of thesubject defrosting system, it must be remembered that time starts thedefrosting cycle while temperature stops the defrosting cycle. Otherwisestated, the time control mechanism 43 will operate to start thedefrosting cycle in accordance with a. predetermined setting which maybe manually variable in accordance with the desires of the user or maybe set for operation at a predetermined time every twentyefour hours.The invention contemplates the provision of temperature responsive meanssuch as the thermostat element 44 which is wired in circuit with thetimed control mechanism 43 and which is operable tov stop the defrostingcycle and effect the conditioning of the refrigerating system for normaloperation wherein the conventional cold control thermostat will haveprominent control to regulate operation of the refrigerating systemresponsive to temperature requirements in the food compartment of the.refrigerator.

In accordance with the teachings of the present invention the compressormotor does not run during the defrosting cycle, the interruption of theelectric current to the compressor motor being accomplished by a cammeans forming a part of the timed control mechanism 43 and adapted forpredetermined engagement with portions of the electrical switch 59 toopen this particular circuit, and said electrical switch 59 being heldin this open position by the holding magnet 60 (Fig. 3) which isoperable during the defrosting cycle and which is set in its operationby the timed control mechanism 43. Completion of the defrosting cycleresponsive to. predetermined operation of the thermostat element 44 willeffect inoperation of the holding magnet 60 which is effective to placethe system in condition for normal operation wherein the conventionalcold control thermostat 48 (Fig. 3) will have prominent control.

It is important to understand that the user may start the defrostingcycle at any time by turning the defrost timer dial 61 one completerevolution. This dial is a part of the timed control mechanism 43.Rotation of the dial as aforesaid will start the defrost cycle ashereinbefore described and the defrost cycle will be stoppedautomatically responsive to a predetermined rise in temperature which iseffective to cause operation of the thermostat element 44.

The defrost cycle may be described as follows: When h time on ol m chanm 43 .i pr pe ly p i on d or def osting. h cam me s f m n a P .Qft e imont o mean 3 w ll' eqm en aged wi h P t on o the electrical switch 59 toopen this particular circuit, and

said electrical switch will be held in this open position by the holdingmagnet 60 whereby to cause inoperation of the compressor motor 20 andsimultaneously the heating element 42 associated with the evaporator 22iselectrically charged and operable to heat refrigerant passing throughthe refrigerant conduit 34 because of the close association of theseparts. Otherwise stated, the timed control mechanism 43 controls theoperation of two things automatically and simultaneously. For example,electric current is turned off to the compressor motor 20 and turned onto the heating element 42. Although the compressor motor 20 remains offduring the defrosting cycle, high pressure in the condenser 21 forcesthe liquid refrigerant through the inlet conduit 31 and into theevaporator tubing comprising refrigerant conduits 33, 34, 34a, 36 and37.

It is important to note that the refrigerant is heated twice, once whenit enters the evaporator from the conduit portion 33 and flows into theconduit 34 which is disposed adjacent the heating element 42 as can beseen in Fig. 2, and again after the refrigerant passes through conduits34a and 34b it will return to make a second pass adjacent the heatingelement 42 via the conduit portion 340. As the refrigerant flows throughthe conduit portion 34c it will receive a second charge of heat fortransmission thereof via the vertical leg 36 to the refrigerant conduits37, 37a and 3712.

It is well known that a liquid, when warm, is lighter than when it iscold. Therefore, the refrigerant warmed by the heater 42 as it passesthrough conduit portion 340 tends to rise through conduit 36 While therefrigerant in the accumulator 40 which has been cooled in passingthrough conduit 37, tends to fall through conduit 41, thus causing athermal circulation of the refrigerant which augments the circulationcaused by the refrigerant entering conduit 33 through the inlet conduit31 effected by the higher residual pressure in the condenser.

Although the compressor remains off during the defrosting cycle thereremains a high residual pressure in the condenser which causes acontinuous flow of refrigerant liquid into the refrigerant conduit 33from the refrigerant inlet conduit 31.

It is important that the relative disposition of the inlet conduit 31with respect to the refrigerant conduit 33 be arranged so that the endportions as at 32 of the refrigerant inlet conduit 31 will impart ajet-like action to the refrigerant during the defrosting cycle effectedby the residual high pressure of the refrigerant in the condenserwhereby to cause the warm liquid refrigerant to circulate through thebottom evaporator shelf 35 and then circulate through the ice tray shelf38 above. Recirculation of the refrigerant within the confines of theevaporator 22 is accomplished by the provision of the refrigerantconduit 41 which is connected to and opens from the accumulator forreceipt of refrigerant therefrom whereby to convey the same into theconduit 33 and, because of the jet-like action of the refrigerant comingfrom the end portions of the inlet conduit 31 as at 32, the refrigerantentering the conduit 33 from the conduit 41 will be drawn to move in thedirection of the arrows through the conduit 34 whereupon the cycle isrepeated. Each time the liquid refrigerant passes the heating elementarea and through conduits 34a and 34c and becomes warmer, the rate offlow is again augmented by virtue of the warmed liquid tending to rise.Thus, it can be seen that there is a pronounced circulation ofrefrigerant through the evaporator conduits responsive to the coactionof the jet flow and the heating element in providing warmed liquidrefrigerant.

As is well known, the undesirable frost accumulations sought to beremoved will naturally be disposed on the evaporator walls and on oradjacent to the refrigerant tubes associated with the evaporator. Thus,the heated refrigerant passing through these conduits will quickly meltany frost accumulation and thereby accomplishing the defrosting action.

When the liquid refrigerant reaches a temperature of approximately 32degrees, the ice and frost accumulations will melt rapidly from theevaporator. The length of time for the defrosting cycle will vary inaccordance with the frost accumulation. There are many factors whichgovern the amount of frost accumulation such as, for example, therelative humidity in the room where the refrigerator is used, the numberof times the door is opened, and the amount of uncovered food disposedin the food compartment of the refrigerator. All of these factors have adirect bearing on the amount of frost and frost thickness governs thelength of defrosting time. However, regardless of the time required, icecream, frozen foods and desserts remain frozen during the defrostingcycle. The holding temperature within the freezer or evaporator 22 onlyvaries a few degrees during the defrosting cycle.

During the defrosting cycle the warmed liquid refrigerant circulates inthe conduits associated with the evaporator and does not flow into thecompressor or condenser because refrigerant at defrosting temperaturesis under a lower pressure than the refrigerant in the compressor andcondenser, and it is well known that low pressure refrigerant will notgo into a high pressure area of its own accord.

As the frost accumulation melts and drops away from the evaporator theheating element 42 and the thermostat element 44 rapidly increase intemperature, until the thermostat reaches its predetermined high pointsetting at which temperature the thermostat element 44 opens theelectrical circuit to stop the defrost operation and, simultaneouslytherewith, conditions the refrigerating system for normal operationwhere the conventional cold control thermostat 48 will have prominentcontrol.

Thus, it can be seen, that the subject invention provides an automaticrefrigerator comprising an evaporator unit 22 and having means 48normally controlling the circulation of refrigerant in said evaporatorunit, a heating element 42 disposed adjacent portions of said evaporatorunit 22 and adapted to warm the refrigerant contained in said evaporatorunit, control means 43 operable at predetermined intervals to renderineffective the operation of said normal control means 48 andsimultaneously therewith control energization of said heating element42, and thermal responsive means 44 for controlling the duration of theperiod wherein the operation of the normal control means 48 isineffective and operable to restore control of the circulation ofrefrigerant in said evaporator unit 22 to said normal control means 48.

In Figs. 5 and 6 it can be seen that the fuse 75 com prises aninsulating casing 76 of generally tubular shape, a tubular washer 77formed of rubber-like material the outer periphery of which is adaptedto be press fitted into portions of the casing 70 as illustrated in Fig.4, thereby to prevent axial movement of these parts when finallyassembled in the casing 70, a stud-like terminal 79, a stud 80 formed todefine the shape substantially as illustrated in Fig. 5 and havinga'projecting shank portion 80a, a bushing 81 having a central throughbore 81a adapted to receive the projecting shank portions 80a, a heatresponsive fusible material 82 disposed between the adjacent surfaces ofsaid projecting shank 80a and the through bore 81a to hold theseelements together, said terminal 79 having end portions 83 arranged toproject into the casing 76, and a spring 84 the opposite end portions 85and 86 of which being respectively screwed on the threaded portions ofthe bushing 81 and the threaded end portions 83 of the terminal 79.

It is preferable that the heat responsive fusible material 82 be formedof a eutectic solder having a predetermined melting temperature. Thistype of solder has been selected because it will not soften or flowunder the selected predetermined temperature and upon reaching thistemperature will immediately flow.

A thrust washer 90 is disposed in a recess 91 of the terminal 79 and isin engagement with an end wall of the tubular washer 77 thereby toprevent axial movement toward the left, as seen in Fig. 5, of theterminal 79 responsive to pulling power effected by the spring 84. Inlike manner, in order to prevent relative axial movement of the stud 80there is provided the thrust washer 93 adapted to engage the end wall ofthe casing 76.

The assembly is maintained in position as shown in Fig. during normaloperation, but in the event that the heater or any of the componentparts of the defrosting system should become defective and cause anoverheating of the heater, the heat responsive fusible material 82 willmelt upon reaching the predetermined melting temperature whereupon theconnection between the stud 80 and the bushing 81 will be broken andwith the cooperation and coaction of the pulling power of the spring 84,the bushing will be pulled to the right as shown in Fig. 4, thusbreaking all electrical connections through the heater.

From the foregoing disclosure it may be observed that we have providedan improved defrosting mechanism which efiiciently fulfills the objectsthereof as hereinbefore stated and which provides numerous advantageswhich may be summarized as follows:

1. Structurally simple, efficient and durable;

2. Economical to manufacture and readily adaptable to mass productionmanufacturing principles; and

3. The provision of a defrosting system wherein the actual duration of aselected defrosting interval is automatically varied in accordance withthe requirements of the refrigerator instead of being arbitrarily fixedfor a definite period of time, the start of the defrosting cycle beingdetermined and effected by a timed control mechanism and the stopping ofthe defrosting cycle and the conditioning of the refrigerator for normaloperation being responsive to temperature responsive means such as athermostat element.

While we have illustrated preferred embodiments of our invention, manymodifications may be made without departing from the spirit of theinvention, and we do not wish to be limited to the precise details ofconstruction set forth, but wish to avail ourselves of all changeswithin the scope of the appended claims.

We claim:

1. Refrigerating apparatus comprising means defining an evaporatorhaving a first conduit for refrigerant, a jet in the inlet of saidevaporator refrigerant conduit, an electric circuit including a timedcontrol mechanism and a temperature responsive means and a heatingsource which is disposed adjacent said evaporator refrigerant conduit,and a second conduit for refrigerant interconnected with said firstconduit whereby the refrigerant may be recirculated through said firstconduit, the circulation of the refrigerant in the first evaporatorrefrigerant conduit being responsive to the application of heat from theheat source to the adjacent first evaporator refrigerator conduit andaugmented by said jet.

2. Refrigerating apparatus comprising an evaporator having a firstconduit for refrigerant, an inlet conduit for refrigerant and extendinginto said first conduit forming a jet and defining with said firstconduit an injector, an electric circuit, a heater element in saidcircuit and disposed adjacent said first conduit, timed controlapparatus to control energization of said heater, a temperatureresponsive means in said circuit to control deenergization of saidheater responsive to a predetermined temperature rise, and a thirdconduit for refrigerant effective to recirculate the refrigerant to saidfirst conduit responsive to operation of said heater element.

3. Defrosting mechanism for a refrigerating apparatus comprising anevaporator having refrigerant conduits including inlet and suctiondischarge conduits, a jet in said inlet conduit, a heat source disposedadjacent at least one of said evaporator refrigerant conduits andadapted to warm the refrigerant contained therein, a refrigerant conduitin said evaporator adapted to bypass the suction discharge conduitwhereby the refrigerant will be recirculated within the evaporatorrefrigerant conduits, said recirculation of said refrigerant beingresponsive to operation of said jet coacting with and augmented by theaction of the warmed refrigerant responsive to operation of said heaterelement.

4. Defrosting mechanism for a refrigerating apparatus comprising anevaporator having refrigerant conduits wherein said refrigerants areexpanded during normal operation of the refrigerating system, saidrefrigerant conduits comprising an inlet into the evaporator and asuction conduit, a refrigerant conduit disposed in said evaporatorwhereby the suction conduit is bypassed for recirculation of therefrigerant in said evaporator refrigerant conduits, and a heat sourcedisposed adjacent at least one of said evaporator refrigerant conduitsto warm the refrigerant contained therein to render said recirculationof the refrigerant within the evaporator refrigerant conduits.

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